<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        .box {
            width: 450px;
            display: flex;
            text-align: center;
            line-height: 50px;
        }
        .box span {
            flex: 1;
        }

        .active {
            color: orangered;
        }
    </style>
</head>
<body>
    <div id="app">
       <!-- <h2 v-once>
           {{ message }}
       </h2> -->
    </div>

    <script src="./js/vue.js"></script>
    <script>
         const app = new Vue({
            el: "#app",
            data: {
                message: "我是标题1"
            }
        })

    </script>
</body>
</html>